Current supplies in which a d-c source is serially connected to a load through a choke and a controlled switch are known; the choke has a free-wheeling diode conected in advance thereof--with respect to the load--and a capacitor is located between the choke and the load. A pulse control source controls the ON and OFF cycling of the serially connected controlled switch to control current flow through the load. To determine the actual current flow through the choke, for example in order to limit the current-time integral to a predetermined maximum level, it was previously necessary to provide a measuring shunting circuit across the choke. Such circuits require not only the shunt, but additional circuit components which are comparatively costly and complex.